沂沭断裂带新活动特点

The Recent Activities of the Yishu Fault Zone

一、引言沂沭断裂带是郯庐断裂带的一部分,位于鲁西和苏北平原,沿沂、沭河流域分布,是构造新活动较强烈的地段。早在中生代初期(T—J),该断裂曾发生过左旋平移运动。到了中生代后期(K)断裂产生拉张运动,由四条平行断裂(F1、F2、F3、F4)形成两堑夹一垒的构造格局。进入新第三纪晚期(N2),断裂产生挤压右旋平移运动,在东部地堑产生一条纵贯南北的昌邑-宿迁大断裂,根据它的新活动特点,进一步划分出两个活动段,即:昌邑—夏庄右旋挤压段和钟华山—宿迁挤压右旋段。历史时期有记载的两次大地震,公元前70年安丘7级地震和1668年莒县8.5级地震就发生在昌邑—夏庄右旋挤压段上。

In this paper we have divided the Changyi-Xugian fault into two sections by using a vast amount of practical data: the right-lateral compressive section in the Changyi-Xiazhuang area and the right-lateral compressive section in the Zhonghua mountain-Xuqian area. There arc 20 active faults, 9 basins and some uplifts in the Yishu Falut Zone in Quaternary period. The right-lateral compressive section in the Changyi-Xiazhuang ares is active in Holocene proved by some practical data. It is a fault occurred earthquake. Nine large events (M=7.0) and one large event (M=8.0) occurred in history in the fault zone. The right-lateral compressive section in the Zhonghua-Xuqian area is not active in Holocene, and no earthquake occurred in the history.